the Brookwood quote is disappointing, since he seems to have missed the point: it's not about x86 ISA, but rather the programming model we all know and love. anyone who has spent time rewriting code to suit the moving target of GPUs will appreciate a relatively normal memory model, threads, caches, shared memory and message passing. the Joules-per-flop argument is a good and interesting one, but it naively assumes that every workload is trivially malleable into the rather rigid model that GPUs provide.
the rash of large and relatively power-efficient Bluegene machines also questions the claim that efficient computation requires the GPU model...